The present invention relates to signaling methods for reporting on the status of interfaces through a carrier network. It particularly concerns status signaling for Ethernet interfaces over a SONET/SDH network (Synchronous Optical Network/Synchronous Digital Hierarchy).
In a telecommunication system, such signaling is essential to inform different units that a failure has occurred somewhere on a communication path. It can help a switch for instance to use a different path to circumvent a failed link or equipment. It can also increase the quality of service by not repetitively sending frames to an out-of-service end.
Such signaling is available in many telecommunication systems having a single protocol which integrates specific messages and mechanisms to inform the different network entities of encountered failures.
When the system implemented supports several protocols on different portions, there is a need to adapt the frames from one portion to the characteristics of the other. This can be accomplished with a frame encapsulation mechanism. A procedure called GFP (Generic Framing Procedure) has been recently defined for this purpose by the American National Standards Institute (ANSI) and can be found in the recent draft specification T1×1.5/2000-024R3. It is aimed at defining a generic mechanism to adapt traffic from high-layer client signals over an octet synchronous transport network. For instance it can provide a mapping between some Ethernet frames, as defined in the standard IEEE 802.3, and a SONET/SDH layer. However, GFP does not allow such mapping and transmission for status information about an end-point, like error messages as defined in the IEEE 802.3 Ethernet protocol.
Moreover, as specified in the IEEE standard 802.1Q approved in December 1998, Ethernet networks may support one or more Virtual Local Area Networks (VLANs). An Ethernet frame circulating in such a network may include, after a Medium Access Control (MAC) address, an additional field called tag header or Q-tag which contains a VLAN identifier (VID). Accordingly, a VLAN-aware Ethernet bridge has the ability to perform frame switching based on the VID, deduced either from the physical port from which the incoming frame is received or from the contents of its tag header. A VLAN is used for the layer 2 broadcasting and forwarding of frames within a sub-group of users (subscribers of that VLAN). For example, in a corporation, it is possible to define respective virtual LANs for various departments to enable selective broadcasting and forwarding of information in the layer 2 procedures.
Although Ethernet frames tagged according to the standard 802.1Q can be transported by GFP, nothing is available to allow the signaling of the failure, the removal or the addition of individual VLANs.
An object of this invention is to improve this situation by allowing the signaling of Ethernet VLAN status using GFP.
Another object of the present invention is to define a simple mechanism for signaling of complete Ethernet interface failure through a synchronous network, which does not require modifying Ethernet standards.